Chapter Objectives After completing this chapter you will be able to: Identify the characteristics...

Chapter Objectives

After completing this chapter you will be able to:

Identify the characteristics and features of IPDescribe IP addressingExplain the purpose and operation of different protocols in the

TCP/IP suite, including DNS, ARP, ICMP, TCP, UDP and DHCPUnderstand IPv6

Internet Protocol (IP)

Provides logical 32-bit network addresses

Routes data packets

Connectionless protocol

– No session is established

“Best effort” delivery

Reliability is responsibility of higher-layer protocols and

applications

Fragments and reassembles packets

Host A

Network Interface

IP Fires & Forgets

Reliability & Sequencing

IPRoutes

If Possible

Router

Host B

Network Interface

IP Delivers

as Received

Reliability & Sequencing

PACKET

Fragmented Packet

Internet Protocol (IP)

IP Packet Structure

Source Address

VersionType ofService

Total LengthIHL

Identification Fragment Offset

ProtocolTime to Live Header Checksum

Destination address

PaddingOptions (variable)

32 bits (4 Bytes)

IP header is normally 20 bytes long

Flags

DATA (variable)

D T R UNUSEDPRECEDENCE

D = DelayT = ThroughputR = Reliability

Type of Service (TOS)

3 1 1 1 2

Fragmentation

Router1

Router2MTU =1500

IP Header Original IP Packet data area

IP Hdr 1 Data 1 IP Hdr 2 Data 2 IP Hdr 3 Data 3

MTU = 4500 bytes MTU = 4500 bytes

FDDI FDDIETHERNET

bytes

The IP Address

193.160.1.0

193.160.1.1 193.160.2.1

193.160.2.0

193.160.1.5

193.160.2.83

Binary Format

Dotted Decimal Notation

11000001 10100000 00000001 00000101

193.160.1.5

Converting from Binary to Decimal

1 1 1 1 1 1 11

2627 24 2022 212325

128 248163264 1

Binary Value

Decimal Value

If all bits are set to 1 then the decimal value is 255 i.e. 1+2+4+8+16+32+64+128=255

Traditional IP Address Classes

CLASS A

CLASS B

CLASS C

0

1 0

1 1 0

NET ID

NET ID

NET ID

HOST ID

HOST ID

HOST ID

Number ofNetworks

Hosts perNetwork 1st Octet

Class A 126 16,777,214 1 – 126Class B 16,384 65,534 128 – 191Class C 2,097,152 254 192 - 223

Traditional IP Address Classes (Contd)

Class D– Used for multicast group usage - first 4 high-order bits are 1110

– 1st Octet between 224 and 239

Class E– Reserved for future use - first 5 high-order bits are 11110

1 1 10 Group Identification

Addressing Guidelines

Network ID cannot be 127

– 127 is reserved for loop-back function

Network ID and host ID cannot be 255 (all bits set to 1)

– 255 is a broadcast address

Network ID and host ID cannot be 0 (all bits set to 0)

– O means “this network only”

Host ID must be unique to the network

Private IP Address Space

10.0.0.0 - 10.255.255.255 1 “Class A” network

172.16.0.0 - 172.31.255.255 16 “Class B” networks

192.168.0.0 - 192.168.255.255 256 “Class C” networks

Subnet Mask

Blocks out a portion of the IP address to distinguish the Network ID

from the host ID

Specifies whether the destination’s host IP address is located on a

local network or on a remote network

The source’s IP address is ANDed with its subnet mask. The

destination’s IP address is ANDed with the same subnet mask. If the

result of both ANDing operations match, the destination is local to the

source, that is, it is on the same subnet.

Subnet Mask Example

For example 160.30.20.10 is on the same subnet as 160.30.20.100 if the mask is 255.255.255.0

– Note: 1 AND 1 = 1. Other combinations = 0.

IP Address 10100000 00011110 00010100 00001010

Subnet Mask 11111111 11111111 11111111 00000000

10100000 00011110 00010100 00000000Result

160.30.20.10

255.255.255.0

160.30.20.0

IP Address 10100000 00011110 11001000 01100100

Subnet Mask 11111111 11111111 11111111 00000000

10100000 00011110 00010100 00000000Result

160.30.20.100

255.255.255.0

160.30.20.0

Subnetting

INTERNET

PRIVATE NETWORK

160.30.0.0/24160.30.1.0/24160.30.2.0/24…………….…………….

160.30.254.0/24 160.30.255.0/24

Routing Advertisement

160.30.0.0/16

• Before subnetting: 1 network with approx.. 65 thousand hosts• After subnetting: 256 networks with 254 hosts per subnet

Example: Network with Customised Mask

Allocated IP address space 160.30.0.0/16

8 bits available for subnets and 8 bits available for host

0255 255 255

0000 00001111 1111 1111 1111 1111 1111

No. of Subnets

xxxx xxxx1010 0000 0001 1110 0000 0000160.30.0.x

xxxx xxxx1010 0000 0001 1110 1111 1111160.30.255.x

3-octet mask 255.255.255.0

Maximum of 256 subnets (28)

Network Host

Example: Network with Customised Mask (continued)


8 bits available for subnets and 8 bits available for host

0255 255 255

0000 00001111 1111 1111 1111 1111 1111

No. of hosts

0000 00011010 0000 0001 1110 xxxx xxxx160.30.x.1

1111 11101010 0000 0001 1110 xxxx xxxx160.30.x.254

3-octet mask 255.255.255.0

Maximum of 254 hosts (28 - 2)

Network Host

Subnetting Example

200.200.200.0 255.255.255.0

Network Address Subnet Mask


200.200.200.64

200.200.200.0

62 hosts per network

Note: Subnet mask for each subnet = 255.255.255.192

200.200.200.192

200.200.200.128

Example Network with VLSM

Allocated IP address space 200.200.200.0/24 Required: 2 subnets with 50 hosts and 8 subnets with 10 hosts

200.200.200.0

200.200.200.0 /26 (max. of 62 hosts)

200.200.200.64 /26 (max. of 62 hosts)

200.200.200.192 /28 (max. of 14 hosts)200.200.200.208 /28200.200.200.224 /28200.200.200.240 /28

200.200.200.128 /28 (max. of 14 hosts)200.200.200.144 /28200.200.200.160 /28200.200.200.176 /28

Note: Subnet masks /26 = 255.255.255.192/28 = 255.255.255.240

Example Network with VLSM

160.40.140.0 255.255.252.0

160.40.156.0255.255.255.0

160.40.152.0255.255.252.0

160.40.157.12255.255.255.252

160.40.157.4255.255.255.252

LAN 1

LAN 3

LAN 2

160.40.144.0255.255.252.0

160.40.148.0255.255.252.0

Site A

Site CSite B

160.40.156.1

160.40.140.1

160.40.152.1

160.40.157.5

160.40.157.6

160.40.157.13

160.40.157.14 160.40.148.1

160.40.144.1

Variable Length Subnets from 1 to 16CIDR

Prefix-lengthSubnet Mask

# Individual Addresses

# Classful Networks

32 B64 B

128 B1 A or 256 Bs

2 A4 A

2 M4 M8 M

16 M32 M64 M

255.224.0.0255.192.0.0255.128.0.0

255.0.0.0254.0.0.0252.0.0.0

/11/10/9/8/7/6

/4/5

240.0.0.0248.0.0.0

16 A8 A128 M

256 M

64 A32 A

128 A1024 M512 M

2048 M 192.0.0.0224.0.0.0

128.0.0.0/2/3

/1

/16 255.255.0.0 1 B or 256 Cs65,534

4 B2 B

8 B262,142131,070

524,286255.252.0.0255.254.0.0

255.248.0.0/14/15

/1316 B1 M255.240.0.0/12

Variable Length Subnets from 17 to 30

CIDRPrefix-length

Subnet Mask# Individual

Addresses# Classful Networks

1/8 C1/4 C1/2 C1 C2 Cs4 Cs8 Cs

16 Cs32 Cs64 Cs

3062

126254510

1,0222,0464,0948,190

16,382

255.255.255.224255.255.255.192255.255.255.128

255.255.255.0255.255.254.0255.255.252.0255.255.248.0255.255.240.0255.255.224.0255.255.192.0

/27/26/25/24/23/22/21/20/19/18/17 255.255.128.0 128 Cs32,766

1/16 C14255.255.255.240/281/32 C6255.255.255.248/291/64 C2255.255.255.252/30

CIDR Route Aggregation

ISP

The INTERNET200.25.16.0/20

200.25.16.0/24 200.25.17.0/24200.25.18.0/24200.25.19.0/24200.25.20.0/24200.25.21.0/24200.25.22.0/24200.25.23.0/24

200.25.24.0/24 200.25.25.0/24200.25.26.0/24200.25.27.0/24

200.25.28.0/24 200.25.29.0/24

200.25.30.0/24 200.25.31.0/24

200.25.16.0/21

200.25.24.0/22

200.25.28.0/23

200.25.30.0/23

200.25.0.0/16

Company ACompany B

Company C Company D

Subnet ID TablesNo. of Bits

in MaskSubnet Mask

255.255.255.248255.255.255.252

255.255.255.240255.255.255.224255.255.255.192255.255.255.128

255.255.255.0255.255.254.0255.255.252.0255.255.248.0255.255.240.0255.255.224.0255.255.192.0

2930

2827262524232221201918

1617

255.255.0.0255.255.128.0

Subnet IDs

0

0,16,32,48,64,80,96,112,128,144,160,176,192,208,224,240

0,8,16,24,32,40,48,56,64…………….,216,224,232,240,248

0,4,8,12,16,20,24,28,32,…………….236,240,244,248,252

0,2,4,6,8,10,12,14,16,18,…………….246,248,250,252,254

0,1,2,3,4,5,6,7,8,9,10,11,…………….251,252,253,254,255

0, 128

0, 64, 128, 192

0,32,64,96,128,160,192,2243rdOctet

4thOctet

0, 128

0, 64, 128, 192

0,32,64,96,128,160,192,2240,16,32,48,64,80,96,112,128,144,160,176,192,208,224,240

0,8,16,24,32,40,48,56,64…………….,216,224,232,240,248

0,4,8,12,16,20,24,28,32,…………….236,240,244,248,252

DNS - Domain Name System

Internet addresses are hard for humans to remember

- Easy for protocol software to work with.

Symbolic names are more natural for humans

- Hard for protocol software to work with.

HumansProtocol software

185.26.69.125

Kiss.val.com

?

Internet Domain Name Space

int com edu gov mil org net us se ie

Generic Countries

ericsson

eng

Oxford

CS eng

ai Linda

robot

Pizza

cookie 4Star

Krusty

Burger

Domain Name Resolution

com

EricssonJuniper ACC

saleseng research

.

Domain Name Resolution

Root Name Server

Com NameServer

ericsson.com

eng.ericsson.com

LocalNameServer

DNSClient

Recursivequery

1 10

2 34

5

6

7

8

9

Iterativequery

DNS CachingInternet name servers use name caching to reduce the traffic on the

Internet and improve performance

Servers report cached information to clients, but mark it as a non-

authoritative binding

If efficiency is important, the client will choose to accept the non-

authoritative answer and proceed

If accuracy is important the client will choose to contact the authority

and verify that the binding between name and address is still valid

Whenever an authority responds to a request, it includes a Time To

Live (TTL) value in the response that specifies how long it guarantees

the binding to remain

Address Resolution Protocol (ARP)

A source must know a destination’s hardware address before it can

send an IP packet directly to it

ARP is the mechanism that maps IP to hardware addresses

ARP uses a local broadcast to obtain a hardware address dynamically

ARP stores mappings in cache for future use

Static entries can be manually entered into the ARP cache

Address Resolution Protocol (ARP)

Source 160.30.100.2000-AA-00-12-34-56

Destination160.30.100.1000-A0-C9-78-9A-BC

“If your IP address is 160.30.100.10 please send me a reply stating your hardware address”

That’s me and my Hardware address is 00-A0-C9-78-9A-BC

Broadcast

Unicast

Remote Networks

ARP Packet Structure

Sender’s Hardware Address (Octets 0-3)

Protocol Type

Target HA (octets 2 - 5)

32 bits (4 Bytes)

Hardware Type

PLENHLEN Operation code

Sender IP (Octets 0-1)Sender HA (Octets 4-5)

Sender IP (Octets 2-3) Target HA (Octets 0-1)

Target IP (octets 0 - 3)

Variable Length

Reverse Address Resolution Protocol

Reverse ARP is the mechanism that maps hardware addresses to

the IP address

RARP protocol allows a newly booted machine to broadcast its

Ethernet address

The RARP server sees this request and sends back the

corresponding IP address

Internet Control Message Protocol (ICMP)

Reports errors and sends control messages on behalf of IP

ICMP messages are encapsulated within an IP packet

One of the most frequently used debugging tools uses ICMP

ICMP Message Format

Code Checksum

Identifier

Type

Sequence Number

Optional Data

IP Header......

ICMP Message TypesTYPEFIELD ICMP Message Types

03458

1112131415161718

Echo ReplyDestination UnreachableSource QuenchRedirect (change a route)Echo RequestTime exceeded for a packetParameter problem on a packetTimestamp requestTimestamp replyInformation request (obsolete)Information reply (obsolete)Address mask requestAddress mask reply

Echo Request and Reply Message Format

Code = 0 Checksum

Identifier

Type = 8 (or 0)

Sequence Number

Optional Data

IP Header......

These messages test whether a destination is reachable and

responding, by sending ICMP echo requests and receiving back

ICMP echo replies.

This test is carried out by using the “PING” command.

Reports of Unreachable DestinationsCode Value Meaning

012345678

9

1112

Network unreachableHost unreachableProtocol unreachablePort unreachableFragmentation needed and DF setSource route failedDestination network unknownDestination host unknownSource host isolated

Communication with destination network administratively prohibited

Network unreachable for type of service

10Communication with destination host administratively prohibited

Host unreachable for type of service

Traceroute

Traceroute uses ICMP and the TTL field in the IP header, to let us see the route that IP packets follow from one host to another.

Source sends packet with TTL set to 1

First router sends back “time exceeded” message

Source increments TTL counter by 1

Second router on path sends back “time exceeded” message

Process continues until ultimate destination send back “port

unreachable” message.

Source uses the responses to display the route to the destination

Transmission Control Protocol (TCP)

Connection-oriented

Provides logical connections between a pair of processes:– These are uniquely identified using sockets

– Socket = IP address & port number, e.g. FTP is port 21

End-to-End reliable delivery

Implements Flow Control

Transmission Control Protocol (TCP)

Units of data transferred between two devices running TCP

software are called “segments”

Segments are exchanged to do the following:– Establish a connection

– Agree window size

– Transfer data

– Send acknowledgements

– Close connection

TCP Packet Structure

Destination Port

Window

PaddingOptions

32 bits (4 Bytes)

DATA

Source Port

OFFSET

Sequence Number

Reserved

Acknowledgement Number

Flags

Urgent PointerChecksum

Well-known Port Numbers

Port Number

Description

720212325537980

104139

160 -223

EchoFile Transfer Protocol (FTP) dataFile Transfer Protocol (FTP) controlTelnetSimple Mail Transfer Protocol (SMTP)Domain name server (DNS)FingerWorld Wide Web (WWW)X400 Mail SendingNetBIOS session serviceReserved

Establishing a TCP Connection

SYN

SEQ # 1,000Window 8,760 bytes

Max. segment 1,460 bytes

Client Server

SEQ # 3,000ACK # 1,001

Window 8,760 bytesMax. segment 1,460 bytes

ACKSEQ # 1001ACK # 3001

SYN

Positive Acknowledgement with Retransmit

Packet lost

Packet should arriveACK should be sent

Send Packet 1Start Timer

ACK would normally arrive at this time

Timer Expires

Retransmit Packet 1Start Timer

Receive Packet 1Send ACK 2

Receive ACK 2Cancel Timer

Events at Sender Site Network Messages Events at Receiver Site

Sliding Window Protocol

Initial window

Window Slides

Segments 1, 2 and 3acknowledged

Sliding Window Protocol

Send Segment 1

Send Segment 2

Send Segment 3

Receive Segment 1

Receive Segment 2

Receive Segment 3Send ACK 4 for next

segment expected

Data, SEQ#2,000 length=100



ACK#2,200

ACK#2,300

Send ACK 3 for nextsegment expected

Slow Start Algorithm

Slow Start adds another window to the sender's TCP: the congestion window, called "cwnd"

When a new connection is established with a host on another network, the congestion window is initialised to one segment

Each time an ACK is received, the congestion window is increased by one segment

The sender can transmit up to the minimum of the congestion window and the advertised window

Slow Start provides an exponential growth (send one segment, then two, then four, and so on)

The congestion window is flow control imposed by the sender, while the advertised window is flow control imposed by the receiver

Congestion Avoidance and Slow Start algorithm

Initialisation for a given connection sets cwnd to one segment and Slow Start threshold to 65535 bytes

The TCP output routine never sends more than the minimum of cwnd and the receiver's advertised window

When congestion occurs (indicated by a timeout or the reception of duplicate ACKs), one-half of the current window size is saved in ssthresh. Additionally, if the congestion is indicated by a timeout, cwnd is set to one segment (i.e., Slow Start)

When new data is acknowledged by the other end, increase cwnd

Congestion Avoidance and Slow Start algorithm (Contd)

The way that the cwnd is increased depends on whether TCP is

performing Slow Start or Congestion Avoidance

If cwnd is less than or equal to ssthresh, TCP is in Slow Start;

otherwise TCP is performing Congestion Avoidance

Slow Start continues until TCP is halfway to where it was when

congestion occurred, and then Congestion Avoidance takes over

Slow Start sends one segment, then two, then four, and so on

Congestion Avoidance dictates that cwnd be incremented by

segsize*segsize/cwnd each time an ACK is received

This is a linear growth of cwnd, compared to Slow Start's

exponential growth

Fast Retransmit

TCP may generate an immediate acknowledgement (a duplicate ACK) when an out-of-order segment is received

The purpose of this duplicate ACK is to let the other end know that a segment was received out of order, and to tell it what sequence number is expected

Since TCP does not know whether a duplicate ACK is caused by a lost segment or just a reordering of segments, it waits for a small number of duplicate ACKs to be received

If three or more duplicate ACKs are received in a row, it is a strong indication that a segment has been lost

TCP then performs a retransmission of what appears to be the missing segment, without waiting for a retransmission timer to expire

Fast Recovery Algorithm

After Fast Retransmit sends what appears to be the missing

segment, Congestion Avoidance, but not Slow Start is performed

The reason for not performing Slow Start in this case is that the

receipt of the duplicate ACKs tells TCP that there is still data

flowing between the two ends

TCP can thus avoid reducing the flow abruptly by not going into

Slow Start

The Fast Retransmit and Fast Recovery algorithms are usually

implemented together

User Datagram Protocol

Connectionless– No session is established

Does not guarantee delivery– No sequence numbers– No acknowledgements

Reliability is the responsibility of the applicationUses port numbers as end points to communicate

User Datagram Protocol

UDP Packet Format

Checksum performed on Pseudo-Header

Destination PortSource Port

UDP ChecksumLength

DATA

BOOTP (BOOTstrap Protocol)

A newly booted device may use BOOTP to obtain an IP address, a bootable file address, and configuration information.

– The client initiates a BOOTP request with a broadcast address to all stations on the local network

– The BOOTP server monitors for BOOTP requests (on UDP port 67). – The server looks up the assigned IP address and puts it in the response message. – It also adds the name of the BOOTP server and the name of the appropriate load

file that may be executed. – It may also add other configuration parameters such as the subnet mask and

default gateway. – The client receives the reply (on UDP port 68).– it uses the information supplied by the server to initiate a TFTP get message to the

server specified. – The response to the TFTP get message is an executable load file.

DHCP is an enhanced version of BOOTP

BOOTP Message Format

0 8 16 24 31

BOOT FILE NAME (128 OCTETS0

CLIENT HARDWARE ADDRESS (16 OCTETS)

SERVER HOST NAME (64 OCTETS)

OP HTYPE HLEN HOPSTRANSACTION ID

CLIENT IP ADDRESSYOUR IP ADDRESS

SERVER IP ADDRESSROUTER IP ADDRESS

SECONDS UNUSED

VENDOR-SPECIFIC AREA (64 OCTETS)

Dynamic Host Configuration Protocol - DHCP

Non-DHCP client

DHCP client

DHCP client

DHCPserver

DHCP DatabaseIP Address 1IP Address 2IP Address 3

IP Address 1

IP Address 2

1. Find a DHCP server

2. Offer an address

3. Accept an address

4. Confirmation

DHCP

DHCP supports three mechanisms for IP address allocation:

– Manual allocation

– Automatic allocation

– Dynamic allocation

DHCP OperationDHCPDISCOVER

Source IP address = 0.0.0.0Dest. IP address = 255.255.255.255Hardware address = 00-80-37-12-34-56

Source IP address = 160.30.20.10Dest. IP address = 255.255.255.255Offered IP address = 160.30.20.150Client Hardware address = 00-80-37-12-34-56Subnet mask = 255.255.255.0Length of lease = 72 hoursServer identifier = 160.30.20.10

DHCPOFFER

DHCP OperationSource IP address = 0.0.0.0Dest. IP address = 255.255.255.255Hardware address = 00-80-37-12-34-56Requested IP address = 160.30.20.150Server Identifier = 160.30.20.10

DHCPREQUEST

Source IP address = 160.30.20.10Dest. IP address = 255.255.255.255Offered IP address = 160.30.20.150Client Hardware address 00.80.37.12.34.56Subnet mask = 255.255.255.0Length of lease = 72 hoursServer Identifier = 160.30.20.10DHCP option: router = 160.30.20.1

DHCPACK

DHCP Interaction through Routers

Router

PC DHCPServerDHCP Discover

DHCP Request

DHCP Discover

DHCP Request

DHCP Offer DHCP Offer

DHCP ACK

DHCP ACK

DHCP Message Format

0 8 16 24 31

BOOT FILE NAME (128 OCTETS0

CLIENT HARDWARE ADDRESS (16 OCTETS)

SERVER HOST NAME (64 OCTETS)

OP HTYPE HLEN HOPSTRANSACTION ID

CLIENT IP ADDRESSYOUR IP ADDRESS

SERVER IP ADDRESSROUTER IP ADDRESS

SECONDS FLAGS

OPTIONS (VARIABLE)

IPv4 and IPv6

If IPv4 works so well then why change?

– Dramatically increase the number of IP addresses

– Provide better support for real-time applications

– Security features

8/038 13 LZUBB 108 101/2

New features of IPv6

Address size

– 128-bit addresses

Improved option mechanism

– simplifies and speeds up router processing of IPv6 packets

Address autoconfiguration

– dynamic assignment of IPv6 addresses

Increased addressing flexibility

– anycast address

Support for resource allocation

– labelling of packets to handle specialised traffic

Security capabilities

– authentication and privacy

8/038 13 LZUBB 108 101/3

The IPv6 Packet Format

BaseHeader

ExtensionHeader 1

ExtensionHeader N

Data area…...

Optional40 bytes

IPv4 Header

Source Address

VersionType ofService

Total LengthIHL

Identification Fragment Offset

ProtocolTime to Live Header Checksum

Destination address

PaddingOptions (variable)

32 bits (4 Bytes)

IP header is normally 20 bytes long

Flags

DATA (variable)

IPv6 Base Header

Version Priority Flow Label

Payload Length Next Header Hop Limit

Source Address

Destination Address

0 4 8 16 24 32

10 x

32

bits

= 4

0 oc

tets

IPv6 Extension Header

Hop-by-hop options

Extension header Description

Miscellaneous information for routers

Routing

Fragmentation

Authentication

Encrypted security payload

Destination options -2

Full or partial route to follow

Management of datagram fragments

Verification of the sender’s identity

Information about the encrypted contents

Additional information for the final destination only

Destination options -1 Information for 1st destination

Hop-by-hop Options & Destination Options Headers

Hop-by-hop Options Header

– Read by all routers along the path

– useful for transmitting management information or debugging commands to

routers

Destination Options Header

– 2 types

one for 1st destination

one for final destination

Routing Header

Specifies a list of IP addresses that dictate what path a packet will

traverse

Type zero routing headers indicate how intermediate nodes may

forward a packet to the next address in the routing header

– strict forwarding, packets only visit routers listed in the routing header

– loose forwarding, unlisted routers can be visited by a packet

Routing Header Format

Next Header Type

Reserved

Number of Addresses

Strict/loose Bit Map

Next address

1 - 24 Addresses

Fragment Header

Next Header Reserved Fragment Offset Res M

Identification

138 8 12

32

Authentication Header

The authentication header provides authentication and integrity

the authentication header extension to IPv6 ensures that a packet

is actually coming from the host indicated in its source address

ESP- Encrypted Security Payload

Transport Headerand Payload

IPv6Header

ExtensionHeaders ESP Header

IPv6Header

ExtensionHeaders

Transport Mode

Unencrypted Encrypted

Tunnel Mode

Unencrypted Encrypted

IPv6Header

ExtensionHeaders ESP Header

Transport Headerand Payload

IPv6 Addressing

Like IPv4, IPv6 assigns a unique address for each connection

between a computer and a physical network

There are three types of IPv6 addresses:

– Unicast

– Multicast

– Anycast

IPv6 Colon Hexadecimal Notation

Consider a 128-bit number written in dotted decimal notation:

– 105.220.136.100.255.255.255.255.0.0.18.128.140.10.255.255

This number written in hex notation

– 69DC:8864:FFFF:FFFF:0:1280:8C0A:FFFF

Leading zeros within a group can be omitted

One or more groups of 16 zeros can be replaced by a pair of colons

– for example: FF0C:0:0:0:0:0:0:B1 can be written as:

– FF0C::B1

Transition to IPv6

Tunnelling

– Configured

manually configuration of IPv6/IPv4 mappings

whole IPv6 address space can be used

– Automatic

compatible address space

no advantage of the extended address space

Chapter Objectives After completing this chapter you will be able to: Identify the characteristics...

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Transcript of Chapter Objectives After completing this chapter you will be able to: Identify the characteristics...